Invasive Control - Misc Forbs

In many instances, the simple task of hand pulling is the most effective way of eliminating unwanted plants.  This pile of invasive Sweet Clover, Wild Carrot and Oxeye Daisy was removed from a one acre barrens opening this past summer.  Remnants of last year’s plant collection can be seen beneath this year’s greenery.

This area is typical of the Blue Jay Barrens openings.  Steep, shallow, extremely dry soils present numerous challenges to plant growth.  Invasive plants can become established, but not with the ease or rapidity demonstrated in the former cropland areas.

The welcome mat for invasive plants is in the form of exposed soil, a defining quality of barrens sites.  A seedling that overcomes the other obstacles can grow undisturbed by competing vegetation.  Colonization may be slow, but a persistent species can build quite a population over a period of years.

This is my fourth year of pulling Sweet Clover and Wild Carrot from this site.  Plant removal is quite an effective control method for these species.  They are biennials that form a rosette in year one, then produce seed and die in year two.  If you can halt the production of seed, you can eliminate new generations of plants.  An annual maintenance visit to each site is still necessary to catch any new plants that may emerge.  Sites that I began treating 10+ years ago, now have only a few Sweet Clover plants per acre and virtually no Wild Carrot.  Sweet Clover seed is notorious for persisting in the soil seed bank and remaining viable for decades after falling from the plant.  In order for the seeds to survive for that length of time, they need to be incorporated within the soil profile where they are protected by the ravages of weather and other environmental factors.  I’ve noticed that most of the studies of Sweet Clover seed longevity have been completed on former crop ground, where fresh clover seed could have been neatly buried by common agricultural tillage practices.  Seed produced on the barrens is unlikely to get buried to a depth that would allow it to be protected for extended periods of time.  The seed here stays near the surface and either germinates or dies, so removing plants rapidly produces positive results.

I’ve also been getting more hands-on with the invasive Oxeye Daisy.

I’m still looking for an effective control method in the old crop fields.  The plant is too numerous and too crowded by prairie plants to be easily removed by hand.  There are also too many quality native plants here to make herbicides a viable control alternative.

This Ragged Fringed Orchid, Habenaria lacera, visible in the center or the preceding photo, is just one of many unassuming plants that has found itself being pressured by Oxeye Daisy.

Oxeye Daisy has been slowly making its way into the barrens.  I hand pulled the daisy from a few test areas two years ago, with favorable results.  This year I pulled Oxeye Daisy right along with the clover and carrot.  New daisy plants begin as a basal rosette.  When they’ve stored enough energy, they send up a flower stalk.

Oxeye Daisy removal is totally effective if you leave no viable plant parts in the soil.  This young plant pulled easily and shows no evidence of missing underground parts.

A slightly older plant displays the start of a rhizome that would eventually give rise to new plants.  The stub of a broken rhizome on a pulled plant means that a viable plant part has been left behind to grow a new plant next year.

A single plant will eventually produce a thick colony of plants.  This plant has a single tall flower stalk and three healthy rhizomes.  I think I’ll be able to successfully eliminate Oxeye Daisy from the more rugged barren sites, but I’m still looking for viable control options in other areas.

I’m still collecting seed heads from Teasel in early August, but I also now treat random plants while I’m out doing other invasive species work.  A shot of glyphosate into the center of a basal rosette will kill the plant, or at least damage it enough that it never produces a flower.  Tall plants can be cut and the stump given a little spray of glyphosate.  These two methods would be difficult to apply on a large scale, but are handy to use when finding a handful of plants in an isolated location.  It’s easier to eliminate the plant at the time it is found, than it is to remember to revisit that spot later on to collect seed heads.

Of course, I’m always interested in animals that feed on invasive plants.  I found this stalk borer inside the base of a tall Teasel plant.  I doubt the borer would have killed the plant, but similar borers might be the reason I occasionally find plants broken off at the base.  These broken plants may lay down and hide in the tall grass, but the flower stalks turn upward and still produce plenty of seeds.  Since I have trouble finding these fallen plants, the borer may actually be hindering my control efforts.  Despite minor setbacks, I’m sure that I can eventually get most of these invasive plants under control.

Prairie Garden Mowing

The tall grass in the Prairie Garden looks a bit battered from the heavy snows it endured this winter.  The combination of strong west winds, heavy snow, and no support outside the garden boundary, caused much of the grass to be laid on its side.  Even though there are acres of similar habitat very close by, birds and other animals spend a lot of time foraging and hiding in this small plot.  This is one of the reasons I leave the garden untouched through the winter.

The new portion of the Prairie Garden has little prairie grass, so the dead stalks of various wild flowers are easy to see.  Birds have pretty much picked the area clean of seeds.

In the spring, I remove the dead top growth.  The process begins by cutting with the brush mower and raking the cut material from the garden.

The clearing away of dead material is done primarily to give me an unobstructed view of the developing plant life.  I intentionally crowded a large number of species into this small space.  They all grow naturally at Blue Jay Barrens, but it takes a bit of a walk to visit all of the areas where the different species occur.  The Prairie Garden specimens make it possible to easily visit the plants every day and follow the various stages of their development.  The recent heavy snow cover has slowed the emergence of many of the common plants.  Some species, such as this Orange Coneflower, Rudbeckia fulgida, were already green and growing prior to the onset of snow.

Monarda has produced this growth in just the week or so since the snow melted.

The invasive Oxeye Daisy, Chrysanthemum leucanthemum, legally designated as a noxious weed in Ohio, maintains a cluster of green basal leaves through the winter.  This is the only specimen found in the garden this spring.  

I’ve been pulling Oxeye Daisy from the Prairie Garden to evaluate the effectiveness of this method in controlling the weed.  I’ve found that the pulled plant can be killed if all segments of the spreading rhizome are removed from the ground.  Fibrous roots don’t seem capable of regrowing the plant, but any small segment of rhizome will quickly reestablish the infestation.  Pulling isn’t a practical method of dealing with fields already filled with Oxeye Daisy, but it can be effective in dealing with new incursions into previously uninfested areas.

After raking, I go over the garden with a push mower equipped with a grass catching bag.  It’s at this stage in my management efforts that some people get the impression that I’m finally getting rid of the weed patch in my yard in favor of a cleanly mowed look.

It is now easy to see anything growing in the garden area.

The material removed from the Prairie Garden is hauled back to the vegetable garden and used as mulch between the raised growing beds.  By next fall, the material will be well composted and will be incorporated on top of the beds.

Pulling Sweet Clover and Other Invasives

During the time of active plant growth in the prairies, I try to avoid management activities that are likely to disturb the Blue Jay Barrens flora.  Jobs such as mowing or the cutting and dragging of brush are performed during the fall and winter, when the plants are in decline or already dormant.  There are some jobs however, that must be done in the middle of the growing season.  One of those is the removal of Sweet Clover from the fields.

Sweet Clover is a tall growing biennial invasive plant that can overtop and out compete many native species.  This prairie opening was once the site of a healthy infestation of Sweet Clover.  Annual removal of the invasive species prior to seed development has resulted in a site that is almost clover free.

Two species of Sweet Clover, White and Yellow, are found at Blue Jay Barrens.  Yellow is the earlier bloomer, but White is not far behind.  The most effective method I have found of dealing with this plant is to physically pull it from the ground.  Clover pulling season begins around the last week of June and continues into late July.  I search through the open field areas and remove every Sweet Clover plant I can find.  This has been an annual activity for several years and in most locations the clover is present only as widely scattered individual stalks.  It’s fairly easy to move around the field and deal with the clover without trampling too much of the surrounding vegetation.  During my first few years of this activity, the clover was so abundant my trampling gave the appearance that a herd of cattle had run through the field.

I also pull a few other invasive species while targeting the Sweet Clover.  Queen Anne’s Lace is another biennial that can be effectively controlled by annual plant removal.  Some people prefer the name Wild Carrot, but I think that name makes it sound like the plant somehow belongs here.  I prefer a name that reminds of its exotic origin.  Now that the Sweet Clover is so reduced in number, I can give more time to removing the Queen Anne’s Lace.  I also pull Oxeye Daisy from the more established prairie areas.  Older Oxeye Daisy plants, those that have begun to send out rhizomes, cannot be pulled without leaving growing bits behind.  During its first year of growth, the plant is composed of a single stalk and its associated root system and can be removed in its entirety.  Hopefully I’ll be able to stop Oxeye Daisy from moving into new territory.

All of the pulled plants are deposited onto one of the established brush piles.  There’s always a chance that some of the plants have been able to develop viable seeds prior to being pulled, so I don’t leave any pulled plants in the field.  If there are seeds in the bunch, they will fall down through the brush pile and have a very poor chance of ever producing a mature plant.

I was particularly troubled to discover Crown Vetch growing in one of the prairie openings.  Crown Vetch is a notorious invasive plant that was once commonly planted on steep road banks.  The road bordering Blue Jay Barrens was so treated in the late 1970’s and I am constantly dealing with Crown Vetch flair-ups in the fields near the road.  The really disturbing part about finding Crown Vetch in this location is the fact that this opening is far from the road and in a watershed that does not come close to the road.  When an invader comes from an identifiable source and travels a particular route, such as down hill or down stream, you can anticipate where it is likely to occur and plan for those events.  An incursion this far outside the predicted pattern makes me fear that Crown Vetch could be a threat to any part of the property.

Crown Vetch is a perennial plant that can not be controlled by pulling.  The stem has a weak point at ground level that allows it to break away rather pull up the roots.  The roots are left in place to grow a new plant.  This is a common feature of many plant species and allows them to survive in areas that receive heavy grazing pressure.  If this infestation was in an old crop field, I would just spray it with glyphosate.  Being in an area that I consider a higher quality prairie, I didn’t want any collateral plant damage.  I chose to clip the Crown Vetch stalks about an inch above the ground and apply concentrated glyphosate directly to the stump. This is a more tedious process, but the result is the death of the vetch and an unblemished prairie.

Some of the old crop fields, especially areas near the house, present a slightly different set of problems.  There is a point where the quantity of Sweet Clover makes hand removal impractical.  If this little corner was the extent of my management area, I could certainly wade in and pull each one of those thousands of clover plants.  This calls for a different management strategy.  In order to reduce the number of clover plants, the plants must be denied the opportunity to produce seed.  An alternative to pulling the entire plant is the removal of the flower.  I accomplished that task on June 16 by mowing this part of the field.

At the time of the mowing, I wondered how much the clover plants would regrow after being cut.  So far, the clover has failed to return.  The native plants, primarily Indian Grass, are regrowing nicely.  Hopefully, mowing will bring the number of Sweet Clover plants down to a more manageable level.

I’m always watchful of biological controls that may be working on invasive plants.  This handsome caterpillar was busy munching away on one of the Yellow Sweet Clover plants.  I identified it as the larva of the Hitched Arches moth.  It appears that this moth eats a wide range of plant species and is not a super Sweet Clover predator.  It may not help me with my task, but it was nice to share the field with this small helper.

Oxeye Daisy

After mowing a field in the winter, I should be able to enjoy the greening of the field in the spring followed by the prairie flowers of summer that are slowly hidden by the late summer tall grasses. All of those things will occur this year, but they are being joined by an unwelcome event. Those patches of white in the field aren’t reflections of clouds. They are rafts of Oxeye Daisy, Chrysanthemum leucanthemum, that have invaded the fields. It may be a favorite flower of many people, but Ohio Revised Code officially lists it as a noxious weed. It’s discouraging to have someone look at your field, point to the Oxeye Daisies and say “Oh, aren’t those beautiful. Where can I get plants like that?”

I was on a naturalist led hike about 25 years ago and commented on Oxeye Daisy growing in one of the Ohio barrens. I was told that it wasn’t a concern because it just filled in the voids and didn’t seem to be displacing any of the native flora. I think we’ve now learned that to be an inaccurate observation. This field is not one that you would consider to have voids. What it had was an opportunity for this aggressive early season plant to establish itself before the warm season prairie species began to grow.

Oxeye Daisy does have a nice flower and many people welcome it into their fields for that reason. This is the one flower that I told my kids they could pick at any time without asking. Picking obviously didn’t slow down the spread. Each flower head will produce many hundreds of seeds, all of which easily produce new plants.

Besides being an excellent seed producer, Oxeye Daisy is a perennial that can spread by the production of rhizomes. Once a plant is established, it proceeds to expand into the surrounding areas. The plant is easily pulled because of its shallow root system, but any rhizome pieces left in the soil quickly produce new plants.

This is going to be a tough plant to deal with. Spraying won’t work because too many other plants would be affected. Pulling, if you had the time and manpower for the job, would not work because you would always be leaving bits of rhizome to grow back. Mowing during the growing season would probably favor Oxeye Daisy, because it easily grows back from the basal stems. Goats would favor the Oxeye Daisy over most early growing plants and could reduce the number of plants over time. Maybe I’ll get a couple of goats and let them work on the areas of worst infestation. I guess I’ll have to find time in my schedule to try out a few control strategies on this newest invader.